Part 1. Power.
Quote:
Originally Posted by zeekat
Complete description for Scarlett's headphone out (meant Scarlett instead of Sapphire, sorry):
Dynamic Range: 107 dB (A-Weighted)
THD+N: <0.002% (minimum gain, -1dBFS input with 22Hz/22kHz bandpass filter)
Maximum Output Level: > +10dBu
Impedance: 10 Ω
Assumed only impedance and max output would hint how loud the output will be, my limited knowledge tells me "dynamic range" would be just signal to noise ratio and THD will be, well, distortion.
This is really crappy when spec sheets on manufacturer are so useless (or at least pretty damn obscure and requiring doing assumptions and own calculations).
Loved Ethan Winers talk on audio myths - will try to watch this one, but there's a chance I won't understand much from it  |
OK, +10dBu. We can use this handy calculator:
http://www.sengpielaudio.com/calculator-db-volt.htm
to see that +10dBu = 2.449489742 V rms.
OK, we know voltage. To figure out current, and then be able to multiply the voltage by the current to determine power in W rms, we can use this calculator:
http://www.ohmslawcalculator.com/ohms-law-calculator
So we punch in 2.449489742 V rms, and then input the specific impedance you want to test with.
This will give us figures for current and watts.
At 32 ohms current I=76.5 mAmps rms.
Power is W=0.1875 W rms. 0.1875 W rms = 187 mW rms.
If you were using 600 Ohm headphones the figures would look like this:
current I=4.08 mAmps rms.
watts W=0.01 W rms. 0.01 W rms= 10mW rms.
Not much compared to serious headphone amps that often have 600mW or more power.
But, reality check time.
We're taking it on faith that the headphone amp can actually produce 2.449489742 V without distorting.
OK, to keep it simple, lets assume it can do what it says on the box.
We did two calculations, for 32 ohms, and for 600 ohms. The 600 ohm calculation has a much greater probability of being accurate than the calculation done at 32 ohms.
This is because at 600 ohms, the chance of having too much current flowing for the amp to handle without distorting is low. We can be pretty certain that if the stated voltage capability is correct, that the power calculations will reflect reality.
It is much less certain at 32 ohms. There is 19 times a much current flowing as there is into a 600 ohm load. Can the amp do it? No idea, because they don't specify maximum current capabilities for the amp.